Conventional tandem bicycles include drive systems that provide a direct linkage between the pedals of the front rider, or captain, and the rear rider, or stoker. The direct linkage results in a pedaling system in which both the captain and stoker must start and stop pedaling at the same time, and generally pedal at the same cadence. The captain and stoker must also start at the same place of a stroke. A directly linked pedaling system can be quite difficult to master for an inexperienced cycling pair or a cycling pair with different physical capabilities. The cycling pair must be able to effectively communicate to execute pedaling functions, such as coming to a stop or adjusting toe straps. Moreover, the cycling pair must always maintain the same cadence while pedaling. Because the pedals are linked, one rider cannot rest while the other rider maintains the speed of the bike. As a result, a captain and stoker having different levels of fitness often find that they are unable to ride at a rate where both riders are comfortable.
Bicycle manufacturers have recognized that it would be advantageous to allow a rider on a tandem bicycle to pedal independently of a partner, and have attempted to design drive systems that would accomplish such a goal. One proposed system to allow a tandem rider to stop pedaling while the other continues pedaling is a jack-shaft system, such as the system disclosed in U.S. Pat. No. 4,502,705 to Weaver. As shown in Weaver, the jack-shaft system adds an intermediate hub that is linked to a front crank assembly by a first chain, and to a rear crank assembly by a second chain. The rear crank assembly is coupled to a freewheel rear hub by a third chain. The use of the intermediate hub allows the rear crank assembly to rotate while the front crank assembly is not rotating.
While the jack-shaft system suggested in Weaver is an improvement over conventional drive systems in tandem bicycles, the jack-shaft system still retains several shortcomings. For example, the jack-shaft system adds a third shaft and chain to the tandem bicycle which increases the weight of the bicycle. The increase in weight makes the bicycle more difficult to pedal and less maneuverable during operation. The jack-shaft system is quite complex, and, as any rider knows, the more complex the system, the greater the chance that a malfunction will occur. The cost of a jack-shaft system is also significantly more than that of a conventional drive system, since an additional shaft, chain, and chainrings must be added to the tandem bicycle.
Another disadvantage of the jack-shaft system disclosed in Weaver is that the tandem bicycle frame must be constructed to accept the jack-shaft. Jack-shaft systems therefore cannot be easily retrofitted onto existing tandem bicycles.
An even greater shortcoming of the jack-shaft system, however, is that the jack-shaft only partially solves the problem of directly linked pedaling by the stoker or the captain. In the system disclosed in Weaver, the captain cannot stop pedaling unless the stoker stops pedaling. Consequently, only the stoker may rest during the pedaling process. If the captain stops pedaling, the stoker must also stop pedaling.
The present invention is directed to overcoming the foregoing and other disadvantages. More specifically, the present invention is directed to providing a system that allows independent pedaling by the captain and stoker on a tandem bicycle.